Metal powders and metal oxides have been employed as microgranular magnetic powders in high-density magnetic recording media in recent years. However, the surfaces of metal powders and metal oxides are hydrophilic, resulting in low affinity for the cyclohexanone, methyl ethyl ketone, and the like employed as solvents for magnetic liquids. Accordingly, it has been proposed that various organic substances having skeletons with high affinity for solvents and adsorptive polar groups be added as dispersing agents and adsorbed to the surface of magnetic powder particles to increase the affinity of the magnetic powder surface to the solvent, thereby increasing wettability by the solvent and promoting dispersion. For example, Japanese Unexamined Patent Publication (KOKAI) Heisei No. 5-62162, Heisei No. 7-21546, and 2001-134922 propose such technique. The contents of these applications are expressly incorporated herein by reference in their entirety.
However, the substances that conventionally have been employed as dispersing agents have themselves had inadequate solvent solubility, making it impossible to ensure adequate adsorption to the surface of magnetic powder. Further, in addition to the functions of adsorbing to the surface of the magnetic powder particles and enhancing solvent affinity, conventional dispersing agents have been inadequate with regard to the function of increasing affinity to organic polymers such as polyurethane that are added as binders and promoting adsorption of these polymers to the magnetic powder surface. Thus, it has been difficult to ensure the electromagnetic characteristics demanded of high-density magnetic recording media in recent years.